Abstract
Milk oligosaccharides (OSs) are bioactive components known to influence neonatal development. These compounds have specific physiological functions acting as prebiotics, immune system modulators, and enhancing intestine and brain development. The pig is a commonly used model for studying human nutrition, and there is interest in quantifying OS composition of porcine milk across lactation compared with human milk. In this study, we hypothesized that OS and sialic acid (SA) composition of porcine milk would be influenced by stage of lactation. Up to 250 mL of milk were collected from seven sows at each of three time points: day 0 (colostrum), days 7-9 (mature), and days 17-19 (weaning). Colostrum was collected within 6 h of farrowing and 3-day intervals were used for mature and weaning milk to ensure representative sampling. Milk samples were analyzed for OS profiles by Nano-LC Chip-QTOF MS, OS concentrations via HPAEC-PAD, and SA (total and free) was assessed by enzymatic reaction fluorescence detection. Sixty unique OSs were identified in porcine milk. Neutral OSs were the most abundant at each lactation stage (69-81%), followed by acidic-sialylated OSs (16-29%) and neutral-fucosylated OSs (2-4%). As lactation progressed, acidic OSs decreased (P = 0.003), whereas neutral-fucosylated (P < 0.001) and neutral OSs (P = 0.003) increased throughout lactation. Six OSs were present in all samples analyzed across lactation [lacto-N-difucohexaose I (LNDFH-I), 2'-fucosyllactose (2'-FL), lacto-N-fucopentaose I (LNFP-I), lacto-N-neohexaose (LNnH), α1-3,β-4-d-galactotriose (3-Hex), 3'-sialyllactose (3'-SL)], while LDFT was present only in colostrum samples. Analysis of individual OS concentrations indicated differences (P = 0.023) between days 0 and 7. Conversely, between days 7 and 18, OS concentrations remained stable with only LNnH (P < 0.001) and LNDFH-I (P = 0.002) decreasing over this period. Analysis of free SA indicated a decrease (P < 0.001) as lactation progressed, while bound (P < 0.001) and total (P < 0.001) SA increased across lactation. Concentrations of OS differ between colostrum and mature milk in the pig, and SA concentrations shift from free to bound forms as lactation progresses. Our results suggest that although porcine milk OS concentration and the number of structures is lower than human milk, the OS profile appears to be closer to human milk rather than to bovine milk, based on previously published profiles.
Highlights
The gastrointestinal tract is known to directly influence physiology of the entire organism
Because the piglet is a widely used model for human infant nutrition, it is necessary to understand how the OS composition of porcine milk compares to human milk
Similar to what is reported for human milk, only a few OS contributed to the majority of the OS abundance in porcine milk
Summary
The gastrointestinal tract is known to directly influence physiology of the entire organism. Gut maturation is influenced by oligosaccharides (OSs) present in the mother’s milk and OS composition of human milk changes throughout lactation, which likely has specific physiological implications in the developing infant. There is interest in characterizing the bioactive components present in porcine milk that could modulate later gastrointestinal development, affording a meaningful comparison with human and other mammal’s milk composition. By understanding the similarities between porcine and human milk OS composition, researchers will be able to elucidate how specific OS aid in the development of the gastrointestinal tract. Milk oligosaccharides (OSs) are bioactive components known to influence neonatal development. These compounds have specific physiological functions acting as prebiotics, immune system modulators, and enhancing intestine and brain development
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